1. Field of the Invention
The present invention relates to methods and compositions to impart coffee stain resistance to polyamide fibers such as those found in textile substrates, as well as to the treated fibers and substrates themselves. More particularly, the present invention relates to compositions useful in imparting coffee stain resistance to polyamide textile substrates, such as carpets, the compositions comprising either (i) a copolymer selected from the group consisting of a hydrolyzed aromatic-containing vinyl ether maleic anhydride copolymer, a half ester of an aromatic-containing vinyl ether maleic anhydride copolymer, and mixtures thereof, or (ii) an aromatic-containing acrylate copolymerized with an acid selected from the group consisting of acrylic acid and maleic acid.
2. The Prior Art
Polyamide textile substrates, such as carpeting and upholstery fabrics, may be permanently discolored or stained by certain colorants, like food or beverage dyes. It is known to use sulfonated aromatic formaldehyde condensates (a) in a yarn finish, during or after fiber quenching (U.S. Pat. No. 4 680 212), (b) in a dye bath (U.S. Pat. No. 4 501 591), or (c) incorporated into the fiber (U.S. Pat. No. 4 579 762, all for the purpose of improving stain resistance of carpet fiber. Use of fluorochemicals in combination with sulfonated aromatic formaldehyde condensates to improve stain and soil resistance is taught in U.S. Pat. No. 4 680 212. Commonly assigned U.S. application Ser. No. 101 652, filed Sept. 28, 1987 (International Publication No. WO 89/02949), discloses improved methods, utilizing application of sulfonated aromatic condensates, to enhance stain resistance of dyed nylon carpet fiber. These documents are all hereby incorporated by reference.
In the prior art the stain blocking performance of compositions is typically determined by testing for resistance to FD&C Red Dye 40, which is found in Cherry Kool-Aid.RTM. drink product, as well as in other beverages and foods. Those compositions which are effective in enhancing the stain resistance of the substrate to FD&C Red Dye 40 are then described as "stain blockers". Applicants have discovered, however, that not all "stain blockers" which are effective against staining by FD&C Red Dye 40 are effective in enhancing the stain resistance of the substrate to coffee.
The present invention was developed as a consequence of a need for a stain blocker which would be effective in resisting hot coffee stains, preferably in addition to resisting Red Dye 40 stains.